1. Field of Invention
The present invention relates to an electrode technology, and more particularly to an extraction electrode contacting with a vanadium oxide or doped vanadium oxide film, which is adapted for the electrode material of the detectors, sensors, optical switches and other devices based on the sensitive material of the vanadium oxide or doped vanadium oxide film.
2. Description of Related Arts
The vanadium oxide film, as a thermal resistance sensitive film, is widely used in fabricating the micro-bolometer un-cooled focal plane array with excellent detection performance and corresponding un-cooled detector, owing to the advantages of (a) low 1/f noise, (b) high TCR (temperature coefficient of resistance) and (c) good technology compatibility with the MEMS process. Furthermore, the vanadium oxide, as a sensitive material, is also used to fabricate the THz detecting focal plane array adapted for THz band (0.1˜10 THz) target detection and identification.
In addition, the vanadium oxide film has an excellent phase transition property at near room temperature. Before and after the phase transition temperature, the conductivity, optical absorption, refractive index, magnetic susceptibility, specific heat and other physical properties of the vanadium oxide film change sharply, so that the vanadium oxide film also has broad application prospects in temperature sensors, gas sensors, solar cell windows, electrochromic devices, optical switches and other fields.
In the high performance detectors, sensors, and other devices, many sensitive units are commonly arranged into an arrayed structure, wherein the specific form thereof depends on the application requirements of the devices. For example, the focal plane array based on the vanadium oxide sensitive film is generally made up of a group of two-dimensional pixel array, wherein every pixel includes a sensitive area and a support structure for supporting the sensitive area. The support structure not only provides the sensitive area with the mechanical support, but also is an important heat transfer path. When the radiation of the detected object is projected to the radiation absorption area of the sensitive unit, the radiation will be absorbed, thus the temperature of the sensitive area will increase. Simultaneously, the heat flows to surrounding environment by means of heat conduction, heat convection and heat radiation. This heat flow will reduce the temperature rise amplitude of the sensitive area, thus reducing the detector response. Accordingly, in order to obtain high detection performance, the array is generally sealed in the vacuum shell, and every pixel in the array is spaced from each other. Therefore, the heat conduction passing through the support structure to the substrate becomes the main heat loss way of the pixel. Moreover, the support structure is also affiliated with electronic conductive paths, namely, pixel electrodes.
To obtain the un-cooled focal plane array with high detection performance, its pixel electrode material generally requires a high electrical conductivity, a low thermal conductivity, a good ohmic contact with the sensitive material, a preparation method with a good compatibility with MEMS and IC processes and so on. At present, the commonly used electrode materials in the vanadium oxide focal plane array are NiCr film, Ti film and so on, among which the NiCr film has become the most commonly used electrode material in the vanadium oxide focal plane array owing to its good oxidation resistance. However, the NiCr film has a large elastic modulus, so that the NiCr film has a large residual stress, thus resulting in the warping of the array unit and other deformations. Furthermore, relatively speaking, the NiCr film has a larger thermal conductivity, so that the detection performance of the vanadium oxide focal plane array is reduced to a certain extent. Therefore, a new electrode material for the vanadium oxide focal plane array is expected to further improve the detection performance of the vanadium oxide focal plane array.
Furthermore, for the manufacturing process of the arrayed sensor, micro-optical switch and other devices based on vanadium oxide, it is important to select an electrode material having an excellent process compatibility with the IC and MEMS processes. The dry etching equipment and etching process commonly used in the traditional IC technological process are difficult to meet the requirement of the NiCr film patterning, so that the process compatibility of the NiCr film electrode is reduced to a certain degree, thus limiting the combination of the manufacturing processes of various devices based on vanadium oxide with the traditional IC process.